Image sampling and color shift correction system in multiple image forming apparatus

Abstract

An image sampling and color shift correction system in a multiple image forming apparatus forms a multiple image by providing a plurality of image output units along a transfer belt. An image control unit applies image data to the image output units. A pattern generator repeatedly generates a register shift measurement pattern in the main scanning direction and the sub-scanning direction of the respective image output units. The register shift measurement pattern is formed outside of the largest paper area. A sampling unit samples an image formed by the respective image output units at both sides of a paper on the transfer belt in the main scanning direction of the transfer belt. A processing unit takes data sampled by the sampling unit and processes the amount of register shift. A control unit controls the image output and image sampling correction.

What is claimed is: 
     
       1. An image sampling and color shift correction system in a multiple image forming apparatus for forming a multiple image by providing a plurality of image output means along a transfer belt, said system comprising: image control means which applies image data to respective said image output means for controlling image formation;   pattern generator means for repeatedly generating a register shift measurement pattern in a main scanning direction and a sub-scanning direction of said respective image output means, the register shift measurement pattern being formed outside the largest paper area;   sampling means for sampling an image formed by said respective image output means at both sides of a paper area on the transfer belt in the main scanning direction of the transfer belt;   processing means which takes data sampled by said sampling means for processing an amount of register shift; and   control means for controlling the image output means and the image sampling means to execute a correction operation in an area between a same one pair of the plurality of image output means.   
     
     
       2. An image sampling and color shift correction system according to claim 1, wherein a sampling is executed based upon a constant amount of turns of a transfer belt during a printing operation. 
     
     
       3. An image sampling and color shift correction system according to claim 1, wherein when the amount of the register shift is outside of a specified range, the printing operation is stopped to execute a correction operation. 
     
     
       4. An image sampling and color shift correction system according to claim 3, wherein after the correction operation is finished, the printing operation is automatically continued. 
     
     
       5. An image sampling and color shift correction system in a multiple image forming apparatus for forming a multiple image by providing a plurality of image output means along a transfer belt, said system comprising: image control means which applies image data to respective said image output means for controlling image formation;   pattern generator means for repeatedly generating a register shift measurement pattern in a main scanning direction and a sub-scanning direction of respective said image output means, the register shift measurement pattern being formed outside the largest paper area;   sampling means for sampling an image formed by said respective image output means at both sides of a paper area on the transfer belt in the main scanning direction of the transfer belt;   processing means which takes data sampled by said sampling means for processing an amount of register shift; and   control means for controlling the image output means and the image sampling means to set a time delay for a correction value write timing operation in respective ones of the plurality of image output means, and to execute a correction operation for all colors in an area between a same one pair of the plurality of image output means.   
     
     
       6. An image sampling and color shift correction system according to claim 5, wherein a sampling is executed based upon a constant amount of turns of a transfer belt during a printing operation. 
     
     
       7. An image sampling and color shift correction system according to claim 5, wherein when the amount of the register shift is outside of a specified range, the printing operation is stopped to execute a correction operation. 
     
     
       8. An image sampling and color shift correction system according to claim 7, wherein after the correction operation is finished, the printing operation is automatically continued. 
     
     
       9. An image sampling and color shift correction system in a multiple image forming apparatus for forming a multiple image by providing a plurality of image output means along a transfer belt, said system comprising: image control means which applies image data to respective said image output means for controlling image formation;   pattern generator means for repeatedly generating a register shift measurement pattern in a main scanning direction and a sub-scanning direction of said respective image output means, the register shift measurement pattern being formed outside the largest paper area;   sampling means for sampling an image formed by said respective image output means at both sides of a paper area on the transfer belt in the main scanning direction of the transfer belt;   processing means which takes data sampled by said sampling means for processing an amount of register shift; and   control means for controlling the image output means and the image sampling means to set a time delay for a correction value write timing operation in respective ones of the plurality of image output means, and to execute a correction operation by skipping an image output means by a required time at the time of correction, thereby executing the correction operation.   
     
     
       10. An image sampling and color shift correction system according to claim 9, wherein a sampling is executed based upon, a constant amount of turns of a transfer belt during a printing operation. 
     
     
       11. An image sampling and color shift correction system according to claim 9, wherein when the amount of the register shift is outside of a specified range, the printing operation is stopped to execute a correction operation. 
     
     
       12. An image sampling and color shift correction system according to claim 11, wherein after the correction operation is finished the printing operation is automatically continued. 
     
     
       13. An image sampling and color shift correction system in a multiple image forming apparatus for forming a multiple image by providing a plurality of image output means along a transfer belt, said system comprising: image control means which applies image data to respective said image output means for controlling image formation;   pattern generator means for repeatedly generating a register shift measurement pattern in a main scanning direction and a sub-scanning direction of said respective image output means, the register shift measurement pattern being formed outside the largest paper area;   sampling means for sampling an image formed by said respective image output means at both sides of a paper area on the transfer belt in the main scanning direction of the transfer belt;   processing means which takes data sampled by said sampling means for processing an amount of register shift; and   control means for controlling the image output means and the image sampling means to set a time delay for a correction value write timing operation in respective ones of the plurality of image output means, and to execute a correction operation by backward shifting at least one of the image output means.   
     
     
       14. An image sampling and color shift correction system according to claim 13, wherein a sampling is executed based upon a constant amount of turns of a transfer belt during a printing operation. 
     
     
       15. An image sampling and color shift correction system according to claim 13, wherein when the amount of the register shift is outside of a specified range, the printing operation is stopped to execute a correction operation. 
     
     
       16. An image sampling and color shift correction system according to claim 15, wherein after the correction operation is finished, the printing operation is automatically continued. 
     
     
       17. An image sampling and color shift correction system in a multiple image forming apparatus for forming a multiple image by providing a plurality of image output means along a transfer belt, said system comprising: image control means which applies image data to respective said image output means for controlling image formation;   pattern generator means for repeatedly generating a register shift measurement pattern in a main scanning direction and a sub-scanning direction of said respective image output means, the register shift measurement pattern being formed outside the largest paper area;   sampling means for sampling an image formed by said respective image output means at both sides of a paper area on the transfer belt in the main scanning direction of the transfer belt;   processing means which takes data sampled by said sampling means for processing an amount of register shift; and   control means for controlling the image output means and the image sampling means to detect a long period oscillation component which is produced for a period longer than one turn of the transfer belt, the detected long period oscillation component being subdivided for respective papers and for short periods within one turn of the belt, and to execute a correction operation in accordance with the detected long period oscillation component.   
     
     
       18. An image sampling and color shift correction system according to claim 17, wherein a sampling is executed based upon a constant amount of turns of a transfer belt during a printing operation. 
     
     
       19. An image sampling and color shift correction system according to claim 17, wherein when the amount of the register shift is outside of a specified range, the printing operation is stopped to execute a correction operation. 
     
     
       20. An image sampling and color shift correction system according to claim 19, wherein after the correction operation is finished, the printing operation is automatically continued.